Add documentation for resolving EHSAN development environment crashes

Add a new file documenting how to resolve EHSAN development environment crashes caused by stale HMR states.

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.agents/memory/MEMORY.md

@@ -1,3 +1,4 @@
 - [Donate semantics](donate-semantics.md) — donations accumulate + clamp to target; a case enters the closed-loop pipeline only when fully funded.
 - [api-server data](api-server-data.md) — mockDb is in-memory and mutated by POST calls; restart the workflow to reset to clean seed for demos.
 - [EHSAN branding](ehsan-branding.md) — ehsan.sa blocks scraping; font is IBM Plex Sans Arabic (best match), currency uses new Saudi Riyal symbol via <Riyal/> mask component.
+- [EHSAN HMR context crash](ehsan-hmr-context-crash.md) — "useLanguage must be used within a LanguageProvider" with correct source = stale Fast Refresh state; restart the web workflow.

.agents/memory/ehsan-hmr-context-crash.md

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+---
+name: EHSAN HMR context crash (false runtime error)
+description: When the POC throws "useLanguage must be used within a LanguageProvider" but the source is correct, it's a stale HMR state — restart the workflow.
+---
+
+# "useLanguage must be used within a LanguageProvider" after edits
+
+If the EHSAN POC crashes with `useLanguage must be used within a LanguageProvider`
+(and/or `Invalid hook call ... more than one copy of React`, or
+`Cannot read properties of undefined`) **while `App.tsx` clearly wraps the tree in
+`LanguageProvider` and the source is correct**, it is almost always a corrupted
+Vite Fast Refresh (HMR) state, NOT a code bug.
+
+**Root cause:** `src/contexts/LanguageContext.tsx` exports both a component
+(`LanguageProvider`) and a hook (`useLanguage`) from one file, so Vite logs
+`Could not Fast Refresh ("useLanguage" export is incompatible)`. After several hot
+updates the running app ends up with a duplicate React context instance and the
+hook can't find the provider.
+
+**Fix:** restart the `artifacts/ehsan-poc: web` workflow. The built/production app
+is unaffected — this is dev-only.
+
+**How to apply:** before editing source to "fix" such an error, confirm the current
+files are actually correct (provider present, key exists); if so, just restart the
+workflow instead of changing code.